1. Field of the Invention
The present invention relates to an ESD protection device that protects an electronic component or an electronic circuit from static electricity, and more particularly relates to an ESD protection device that includes first and second discharge electrodes facing each other across a certain gap in a ceramic multilayer substrate.
2. Description of the Related Art
Various known ESD protection devices 101 have been used to protect semiconductor devices or electronic circuits from static electricity.
For example, an ESD protection device illustrated in FIGS. 9A and 9B is disclosed in WO2008/146514 described below. An ESD protection device 101 includes a ceramic multilayer substrate 102. A cavity 103 is formed in the ceramic multilayer substrate 102. Also, a first discharge electrode 104 and a second discharge electrode 105 are arranged in the ceramic multilayer substrate 102. Tip portions of the first discharge electrode 104 and the second discharge electrode 105 are positioned in the cavity 103. As illustrated in FIG. 9A, the tip portions of the first and second discharge electrodes 104 and 105 face each other across a gap G in the cavity 103. Also, a mixture part 106 is arranged on the underside of the cavity 103. The mixture part 106 is connected to the underside of the first and second discharge electrodes 104 and 105 to connect the first and second discharge electrodes 104 and 105.
Details of the mixture part 106 are as illustrated in FIG. 9B. In the mixture part 106, conductive particles 106a coated with an inorganic material having no electric conductivity are dispersed in a ceramic material.
In the ESD protection device 101 described in WO2008/146514, creeping discharge and aerial discharge between the first and second discharge electrodes 104 and 105, which face into the cavity 103, are utilized. Here, the discharge start voltage is assumed to be adjustable by providing the mixture part 106.
However, in the ESD protection device 101, there is a problem that, when discharge is repeated between the first and second discharge electrodes 104 and 105, the discharge start voltage increases, or discharge does not occur even when static electricity is applied.